I have booked a hotel room in Germany.
On the reservation confirmation, it says:
Room category: 1 × French bed room non-smoking
What is a French bed room?
German double beds are usually equipped with two mattresses. A 'French bed' (französisches Bett), on the other hand, is a bed wide enough for two persons, but equipped only with one mattress.
They are usually narrower than regular double beds, the most common width is 140cm, but not necessarily. If you look into bed shops with a wider selection of products, you can get 120, 140, 160 and 180cm-wide French beds:
Die Breiten variieren von 1,20 bis 1,80 m.
The name allegedly comes from the 'cosier' way French people tend to spend their night. German partners obviously rather stick to 'mine and thine' sides of the bed, with a clear separation line for extra protection.
Some German hotels use this term to refer to a room with a double bed of standard size - 140cm wide. Essentially, the bed sleeps 2 and many people have this size in their homes, but people used to queen- or king-sized beds may find the bed small. It doesn't imply a particular style of decor or arrangement of bedding.
I think this issue arises from sloppy punctuation.
Hotel and motel rooms are commonly described by the size and number of beds contained. Thus, one sees "queen bed room" and "king bed room" and so on.
The OP's room contains one French bed, and thus is a "French bed room."
In hotels, "french bed" usually denotes pretty narrow double bed (meant for TWO persons). It can be as narrow as 140 centimeters and will almost always come with shared duvet. My personal opinion is, that these beds are definitely not meant for sleeping, but for other activities :).
The experience of different people may vary, but I would suggest avoiding this if you need decent space to sleep well. And, of course, such bed is very much not suited for sharing with anyone else except people you are really intimate with.
On the other hand, for a single use, these beds are quite ok.